what ive found out is if its on widescreen (16:9) then the borders at the top and bottom will not be there, but set on standard (4:3) the borders will be there
Thihs happened to me when I played RE4 on the gamecube (I'm sad and have it for both the wii & gc!)
Are you sure the wii is set up on to use the EDTV through the component cable or try to set the Wii up to use a 60hz display?
You can change it in the Wii settings menu, and its the screen type option. (Underneath the widescreen option). If its set at 50hz that might explain the black borders.